OCCASIONALLY the radiologic appearance of a common benign lesion is indistinguishable from a metastatic tumor within the same organ. A case in point is malignant melanoma, metastatic to the breast, which may be identical in appearance to a benign fibroadenoma of the breast. The two following cases demonstrate the impossibility of differentiating these lesions using only physical examination and xerographic confirmation. Report of Cases Case 1.— A 27-year-old woman went to her local physician complaining of a tender lump in the right axilla. After examination, which showed only an axillary mass and two discrete, freely movable "adenomas of the breast," she was referred to a surgeon who felt she probably had a lymphoma. The patient underwent lymph node biopsy of the solitary axillary lymph node, which measured 2×2 cm. The pathologic diagnosis was anaplastic adenocarcinoma, metastatic to the axillary node. The patient was referred to University of Iowa Hospitals and